The answer is simple, albeit controversial: I don't believe in reviews of tabletop games. I mean, I DO believe they exist, since I've seen and read them, of course; but I don't believe in any one person's ability to give a complete and fair review.
To explain this, I'm going to go off on a little bit of a tangent here, so bear with me. You see, art, as it exists in literary and film formats, is static. Two people can watch the same movie and, all other things being equal, will have the same experience. They may differ as to how much they appreciate that experience, but it's the same experience. Videogames are similar in that way...Call of Duty is always Call of Duty, regardless of who you are, how you experience it, and what you expect from it. So all of these things can be fairly reviewed, based on the vision the creators had, and their attempts to actualize that vision. When a seasoned critic...not some random dude on the internet, but a pro, your Roger Eberts, your James Bernardinellis...reviews a film, they are essentially answering the question did this film/book/videogame do what it set out to do? Their entire review is a yes or no answer to that question, and how the critic came to that answer.
That question cannot be answered for tabletop games, however, because tabletop games are fully interactive, in a way videogames are not. The designer of a tabletop game, even a fairly rigid boardgame, can have no complete idea about how their game is going to be played once it's out in the wild. One can play a World of Darkness horror game as slapstick comedy without changing a single rule. The designer may have intended for their game to be horror, but the players are using it for comedy. And if it's working and the players are having fun with it, then the designer did not fail. His product is simply being used in an unintentional way.
Thus, tabletop games are not art. And if you accept my definition of a review as an answer to the question "did it work?", then a tabeltop game cannot be fairly reviewed, because the answer in the case of every tabletop game is "depends on the players."
So, all that being said, I'm going to throw out a couple of caveats, then publish this and get flamed by the entire tabletop community (well I guess I'm being a little arrogant here, as I doubt even 1% of the entire tabletop community reads this). The caveats are as follows:
1. Tabletop reviews do have value. A review of a tabletop RPG/boardgame can serve as a very detailed, very informative evaluation of all the various aspects of that game. It can't answer the question "Will you like it?" because that, as explained before, depends on how you use it, but a review can make some specific statements about the quality of the artwork, the clarity of the rules, the production value, etc.
2. Reviews are a valid way to communicate your feelings on a game. One could argue that a review is just one dude's opinion. If you believe that, then nothing's different for tabletop reviews: it's still just one dude's opinion. The "your mileage may vary" caveat may be much bigger in a tabletop review than other kinds of reviews, but it's still, at the end of the day, your opinion. I can't stress this second caveat enough, because I do believe there is room for two definitions of reviews. So if you happen to believe that a review is indeed nothing more than one dude's opinion, we automatically agree to disagree. (And, incidentially, I apologize that you read an entire blog entry arguing with that definition).
3. Tabletop games aren't art. They're something more. Something better. Alot of people are probably going to be pissed about my denouncement of tabletop gaming as not art, but let's not get out of control here: "not art" doesn't mean "it sucks." It means just that: "not art." Sofas are awesome. But they are not art. A good set of power tools are awesome. But they are not art. A 50-inch LCD TV is awesome. But it aint' art. So it is with tabletop games. I love them more than any human being should ever love an inanimate object. But that doesn't make them art. For what it's worth, I think tabletop games are something better than art, because they foster creativity and interaction with others. Art can do that, too, but tabletop games are designed for it, whereas art, typically, is not.
And, one last caveat:
4. Who the hell am I? I am not Roger Ebert. I am not a game designer. I have not published anything significant, by any definition. Although I do have a Bachelors degree in Writing and am one semester away from a Masters degree in it, I have no specialized knowledge beyond that about what art is, or isn't. I am just one of those random dudes on the internet keeping a blog. So if you disagree with me, all that's fundamentally happened here is this: you don't feel the same way as Some Other Guy. So there's no need to hate. Right? RIGHT?